Single cell multiomics revealed fibrotic trajectories of endometrial cells and interaction with the pro-fibrotic macrophages in intrauterine adhesion

Intrauterine adhesion (IUA) is prevalent in women of childbearing age and can affect pregnancy outcomes or even lead to infertility. Currently, there is no effective clinical cure. We profiled more than 100, 000 human endometrial cells from IUA and normal endometrial tissues using single cell RNA sequencing (scRNA-seq), single nucleus transposase-accessible chromatin sequencing (snATAC-seq) and spatial transcriptomics to gain an in-depth understanding of the cellular and molecular mechanisms underlying IUA pathogenesis and enable the development of therapeutic targets. We investigated the diversity of fibrotic cell populations in human IUA. In addition to myofibroblasts, we identified a novel ACTA2 + KRT8+ myofibrotic-epithelial subpopulation and ACTA2 + CD31+ myofibrotic-endothelial subpopulation. The three fibrotic cell lineages were also detected in the rat IUA model. We also reconstructed the molecular differentiation trajectories and fibrotic molecular characteristics of the multiple fibrotic cell lineages. Extracellular matrix (ECM) related genes and fibrosis-related transcription factors (TFs) were highly expressed in the multiple fibrotic cell lineages in human and rat IUA. Finally, we revealed the pro-fibrotic immune microenvironment of IUA, in which the pro-fibrotic macrophage population was highly enriched in the IUA fibrotic niche and positively correlated with IUA clinical disease features. Macrophages can promote fibrotic gene expression in fibrotic cell populations through SPP1 and GALECTIN9. The changes in the fibrotic immune microenvironment showed high consistency in the human and rat IUA endometrium. Our study resolved the contribution of multiple fibrotic cell lineages and their interactions with the pro-fibrotic macrophages to endometrial fibrosis in IUA and provided therapeutic targets for IUA treatment.